docs: def quoted(arg):
      """ Given a string, return a quoted string as per RFC 3501, section 9.
  
          Implementation copied from https://github.com/mjs/imapclient
          (imapclient/imapclient.py), 3-clause BSD license
      """
      if isinstance(arg, str):
          arg = arg.replace('\\', '\\\\')
          arg = arg.replace('"', '\\"')
          q = '"'
      else:
          arg = arg.replace(b'\\', b'\\\\')
          arg = arg.replace(b'"', b'\\"')
          q = b'"'
      return q + arg + q